f150 5.4 mpg question

[7 point]

I checked my mpg the last couple tanks it's about 15-15.5 I'm happy with that .

 

[bruiserbuckgrower]

I don't have that truck, but because of some fellow automotive techs I'm familiar with the weak points of that engine, it could be your cam phasers have worn out/are wearing out, they're hydraulically operated , and affected by dirty oil also, they are controlled by the computer to adjust the timing , when they wear out you usually hear some noise from the top of the engine, and your timing won't be what it should be, which can drastically change your fuel mileage. Worn oil pumps also contribute to Cam phasers not working right.

To add to this I have a 2010 f150 with the 5.4 and more times than not it is showing or possibly even throwing a code for the cam phasers when in all actuality it is the vvt or vvt solenoid screens that are stopped up. If the truck cranks up runs normal a few minutes and then acts really funny with the rpms dipping really low, especially when stopped at a red light, it's more than likely the solenoid and not the cam phasers. I went round and round with several mechanics and 2 ford dealerships telling me I needed to replace the cam phasers and timing chains and i simply refused to believe them. If it is the phasers it should be doing stupid stuff at every rpm not just an idle. There is an easy test to check this by simply unplugging the vvt solenoid and if the trucks idle events out instantly it's the solenoid not the phasers. The solenoid has a screen that gets stopped up (sounds backwards) but essentially dumps to much oil to the phasers at low idle and it tries to choke the truck off, it throws all sorts of codes leading one to believe it is the cam phaser, the giveaway for vvt is if throws the "over retarded code" (no ****) which in turn throws the cam code, usually a bad bank code and another actuator code. From 04 to 08 it is an easy fix, 09 and 10 you have to remove the valve cover to pull the solenoid

This does not sound like the OP's problem but ford has replaced many unneeded cam phasers for 1600-2400 shop bill when a 100 dollar part is all that is needed. And guess what comes with fords cam phaser kit, shiny new vvt solenoids.